perf hists browser: Add option for runtime switching perf data file

Based on perf report/top/scripts browser integration idea from acme.

This will enable user to runtime switch the data file, when this option
is selected, it will popup all the legal data files in current working
directory, and the filename selected by user is saved in the global
variable "input_name", and a new key 'K_SWITCH_INPUT_DATA' will be
passed back to the built-in command which will perform the switch.

This initial version only enables it for 'perf report'.

v2: rebase to latest 'perf/core' branch (6e1d4dd) of acme's perf tree

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1359873501-24541-1-git-send-email-feng.tang@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>